A coating device known in the art coats a steel wire for a bead core with rubber. For example, patent document 1 discloses a rubber coating device that heats a steel wire using an electromagnetic induction heating coil or a coil heater and extrudes rubber to the heated steel wire. The steel wire is heated in advance. Thus, the rubber contacting the steel wire is softened by heat and applied to the steel wire. This coats the steel wire with the rubber.